Variation and process of life history evolution in insular dwarfism as revealed by a natural experiment

Abstract

Islands offer a classic topic for evolutionary studies. Few other subjects have historically raised as much fascination as the island large mammals that having evolved into dwarfs. Consensus has been gained that multivariate ecological causes are behind those changes, but what remains largely unexplored are the mechanisms behind them: how life history (age of reproduction, growth rate, longevity) change with insular dwarfism. Previous studies produced contrasting results difficult to compare, as they concerned different species in single islands. The Japanese Archipelago offers worldwide a unique natural experiment, as in its numerous islands of different sizes the same group of organisms, deer, have evolved into different sizes. Using an extensive examination of bone microstructure, statistical modelling of growth rate and demography, we demonstrate different degrees of change in life history in different islands. We discovered how different life parameters amount to a new, K-strategy contrasting to that of the parent population.

Palaeohistology reveals a slow pace of life for the dwarfed Sicilian elephant

“…Our results provide evidence that P. falconeri did not shift towards the fast end of the LH continuum by truncation of the growth period, as widely claimed for insular dwarf elephants (P. falconeri 18,21,[23][24][25] and P. cypriotis 26 ) and dwarfed slow-growing dinosaurs (Telmatosaurus and Zalmoxes 27 ). Instead, they agree with the finding of similarly slow molar GRs in the other dwarf Mediterranean elephant, P. cypriotis 32 , and with LH traits seen among other insular dwarf mammals such as Myotragus balearicus [64][65][66] and extant and fossil insular cervids [67][68][69] . In fact, the only empirical evidence for early onset of reproduction in an insular dwarf mammal comes from introduced feral Amsterdam Island cattle 70 and is considered to result from artificial selection 71 .…”

Scaling species interactions: implications for community ecology and biological scaling theory

“…Evidence that increased protection from mortality by predation and other environmental hazards favors longer, slower paced lives is shown by such associations occurring in species with welldeveloped body coverings (e.g., armor, spines, shells) [166] or other protective adaptations (e.g., flight, arboreal lifestyle, or hibernation in refuges) [167][168][169][170] independently of their body size. In addition, on islands where predation is often absent or reduced, and thus intraspecific competition for food is relatively intense, many kinds of species have evolved increased longevity and slower rates of growth and reproduction (e.g., [171][172][173][174][175][176][177][178][179][180][181][182][183][184][185]). This so-called "island syndrome" [173,177,[184][185][186] may also be associated with reduced rates of metabolism [187].…”

Endless bones most beautiful: Book review of Vivian de Buffrénil, Armand J. de Ricqlès, Louise Zylberberg, Kevin Padian (eds) 2021 Vertebrate Skeletal Histology and Paleohistology

“…Large data approaches could contribute to making palohistology more prominent, by discovering phylogenetic and functional patterns (e.g., Hayashi et al, 2020;Rössner et al, 2021;Amson et al 2022). This will require collaborative efforts and coordinating.…”